Loudspeaker devices often include a port, sometimes called a bass reflex port or a vent, to improve speaker output capabilities. A port may be associated with a particular resonant frequency to increase speaker efficiency at the particular frequency. Ports may enable improved speaker output at lower frequency ranges, which may offer greater sound fidelity over the entire frequency spectrum and/or sound better. Some speakers are designed to use multiple ports tuned to multiple frequencies, so as to further improve sound output at the multiple frequencies. Accordingly, ports may allow a speaker enclosure to be designed smaller, lighter, using less expensive materials, and/or having better overall sound quality.
Unfortunately, port usage may generally reduce sound quality under some circumstances. For example, transient sounds may not be faithfully reproduced by a ported speaker. Furthermore, port resonance may introduce undesirable sound artifacts. Additionally, although ports are typically beneficial for efficiency at low frequency ranges, a port may reduce speaker efficiency in other ranges, such as mid-range and/or high range.
A ported loudspeaker may increase speaker efficiency at low frequencies compared to a typical closed box loudspeaker. The physics describing the increase in the low frequency efficiency of a port is called the Helmholz Resonance, characterized by the following equation describing a cylindrical port:
            f      H        =                  υ                  2          ⁢          π                    ⁢                        A                                    V              0                        ⁢            L                                ,where fH is the resonant frequency of the port, υ is the speed of sound in the medium under consideration, A is the cross sectional area of the circular port, V0 is the static volume of the cavity, and L is the length of the port. The equation may be adjusted as necessary to characterize ports of any shape. Proper tuning of the port may extend the low frequency response of a loudspeaker. Multiple ports may be tuned to multiple frequencies to enhance a wide range of frequencies.